Tobacco is the leading cause of preventable death and disease among adults in the U.S. and one-third of all cancers are directly attributable to tobacco use. Minority and underserved populations experience profound tobacco-related disparities because of inequities in access to treatment, the health consequences of tobacco, marketing by tobacco companies, and many other factors. For example, Hispanics are less likely than non-Hispanic whites to receive help from their health care provider during a quit attempt or to have access to pharmacotherapy. Moreover, tobacco is a major public health problem among Hispanics as 3 of the 4 leading causes of death among Hispanics are related to smoking (i.e., cancer, heart disease, stroke). Thus, a cornerstone of disease prevention among Hispanics in the U.S. is reducing tobacco use. Despite the critical importance of reducing smoking in Hispanic populations, the search for effective methods to do so is hampered by the paucity of research on the mechanisms underlying smoking cessation in this population. As noted in one prominent report, "underlying the challenge to eliminate health disparities is the inadequate empirical understanding of the proximal and distal determinants of tobacco use, nicotine addiction, and related consequences among understudied and historically underserved populations" (Eliminating Tobacco- Related Health Disparities: Summary Report). The proposed study addresses this gap. This longitudinal cohort study will examine the influence of neighborhood, individual, and acute intrapersonal and contextual determinants of smoking cessation among adult, Spanish-speaking, Hispanic smokers recruited from the Mexican-American (MA) Cohort Study (N=200). All study procedures, treatment materials, and assessments will be conducted in Spanish. Participants will be tracked from 2 weeks prior to their quit date through 26 weeks post-quit date. They will be assessed for 4 contiguous weeks (1 week precessation through 3 weeks postcessation) using state-of-the-science ecological momentary assessment (EMA) procedures. All participants will receive smoking cessation treatment consisting of nicotine patch therapy, self-help materials, and brief in-person and telephone counseling based on our empirically-validated intervention for Spanish-speaking Hispanic smokers (Wetter et al., in press). There have been exceedingly few studies examining the mechanisms underlying smoking cessation among Spanish-speaking or Hispanic smokers, and to the best of our knowledge, none that that have: (a) investigated the influence of neighborhoods, or (b) included the use of EMA to investigate the acute intrapersonal and contextual influences on the process of quitting. Thus, the proposed study will make a unique contribution to the field, as well as address key recommendations from major reports on smoking among minorities (USDHHS, 1998) and reducing health disparities (USDHHS.2002).